Computed tomography of ureteral obstruction.

Although hydronephrosis can usually be diagnosed by urography and/or pyelography, the etiology of the obstruction may not be apparent. Computed tomography (CT) is usually helpful in evaluation of these cases. In 36 cases in which CT was performed solely to determine the cause of ureteral obstruction of uncertain etiology, it proved to be of value in 33 instances (91.7%). The disease processes encountered in this series included metastatic carcinoma to the ureter or periureteral tissues(22), lymphoma (one), primary ureteral tumor (two), radiolucent ureteral stone (four), adjacent ileocolitis (two), aortic or iliac artery aneurysm (two), fibrous band(one), urinoma (one), and radiation fibrosis (one). In three cases (8.3%) an etiologic diagnosis could not be made by CT. These patients had radiation therapy to treat malignant disease, and recurrent tumor responsible for ureteral obstruction could not be distinguished from radiation fibrosis.